1. Technical Field
The present disclosure relates to methods and devices for fabricating carbon nanotube film, particularly, to a method and a device for drawing a carbon nanotube film from a carbon nanotube array.
2. Description of Related Art
Carbon nanotubes are tubules of carbon generally having a diameter of 0.5 to 100 nanometers, and composed of a number of coaxial cylinders of graphite sheets. Carbon nanotubes have interesting and potentially useful thermal, electrical and mechanical properties, and have recently attracted a great deal of attention for use in different applications such as field emitters, gas storage and separation, chemical sensors, and high strength composites.
However, the main obstacle to an actual application of carbon nanotube use is their difficulty to process, due to the powder form of the carbon nanotube products. Therefore, carbon nanotubes are formed into films to facilitate handling and processing thereof. At present, different methods are widely used for fabricating carbon nanotube films including: a growing method, a spraying method, and a Langmuir-Blodgett (LB) method. By using the growing method, a carbon nanotube film can be grown on a substrate. However, the method typically requires high temperature during the growing process and cannot be applied to substrates made of plastic. By using the spraying method, carbon nanotubes, dispersed in a solvent, are sprayed on a substrate. In this method, however, carbon nanotubes cannot be well-dispersed, due to their tendency to aggregate, and thus, a uniform film is difficult to form. By using the Langmuir-Blodgett (LB) method, carbon nanotubes are made soluble through an introduction of amide groups therein, and then through a step of “molecular self-assembly”, the film accumulates on a substrate. However, the method forms a film of disordered carbon nanotubes, and so many excellent properties of the carbon nanotubes are sacrificed.
Recently, as disclosed by patent application US2008/0248235A1 to Feng et al., a new kind of carbon nanotube film has been fabricated. The carbon nanotube film is directly drawn from a carbon nanotube array by using a tool. This carbon nanotube film is a free standing film for the reason that the adjacent carbon nanotubes are joined end-to-end by van der Waals attractive force therebetween. The carbon nanotubes in the carbon nanotube film are aligned substantially along the same direction parallel to the surface of the film. Therefore, the carbon nanotubes in the carbon nanotube film are orderly arranged, and on the aligned direction of the carbon nanotubes, the carbon nanotube film can achieve good thermal and electrical conductivity. Further, for the reason that the carbon nanotubes are parallel to the surface of the carbon nanotube film, the carbon nanotube film has a high transparency, and is suitable for being used as a transparent conductive film. The carbon nanotube film is fabricated easily by selecting a plurality of carbon nanotubes having a predetermined width using a selecting tool such as a wide adhesive tape to contact the carbon nanotube array; and pulling the carbon nanotubes at an even speed to form the carbon nanotube film. The method is simple and can be easily adopted in practical mass production. Further, the carbon nanotube film is free standing and adhesive, and can be laid and attached most any place desired. Furthermore, the carbon nanotube film is flexible.
However, the quality of the carbon nanotube film, such as uniformity of the carbon nanotubes distributed therein, is largely affected by the selecting tool and defects may be formed in the film as well. The adhesive tape is difficult to be manipulated, and the contacting area between the carbon nanotubes and the adhesive tape is hard to be controlled. Further, the adhesive tape is soft. When the contacting area between the carbon nanotubes and the adhesive tape is relatively small, and the carbon nanotubes are not firmly adhered to the adhesive tape, during the drawing process some of the carbon nanotubes may detach from the adhesive tape, producing a carbon nanotube film with many defects.
What is needed, therefore, is to provide a device for drawing the carbon nanotube film that is capable of effectively increase the contact area between the carbon nanotubes and the device, and a method for drawing the carbon nanotube film by using the device.